OBJECTIVES: The overall objectives of the project are as follows: 1. Production and serological characterization of rabbit and nonhuman primate antisera to human cell membrane antigens. The antigens which distinguish various cell types (e.g. tissue-specific antigens) such as lymphocytes, macrophages and myeloid cells will be emphasized. 2. Isolation and characterization of the human membrane antigens defined by the above antisera. 3. Isolation and characterization of a lymphokine (LAF) released from human monocytes which results in increased thymidine incorporation in mouse thymocytes. 4. Immunological studies on experimentally produced (thymectomized and irradiated) T cell deficient chimpanzees. 5. Characterization of the membrane antigens and cell populations affected in long term, conditioned medium cultures of human T cells.